A convenient and efficient synthesis of a novel class of acyclicnucleosidephosphonates derived from 2-(phosphonomethoxy)propanoic acid has been developed. The key step of the synthesis is the optimized oxidation of the 3-hydroxy-2-(phosphonomethoxy)propyl (HPMP) analogues to the corresponding 2′-carboxy-PME (CPME) derivatives using the TEMPO/NaClO2/NaClO oxidizing system. Although (S)-3-(adenin-